p5pRT
commented
21 years ago From perl-5.8.0@ton.iguana.be
Created by perl-5.8.0@ton.iguana.be
perl -wle '$_="bk"; print"_=$_\,1=$1" while s/((.))k$2//;print"|$1|"' Use of uninitialized value in concatenation (.) or string at -e line 1. _=\,1=b |b|
| perl -wle '$_="bk"; print"_=$_" while s/((.))k$2//;print" | $1 | "' Use of uninitialized value in concatenation (.) or string at -e line 1. _= Use of uninitialized value in concatenation (.) or string at -e line 1. |
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As you can see $1 after the while only exists if it has been used during the loop.
Many other variants of this bug exist. e.g. finding the longest repeated substring (up to length 2**16) like this works:
#!perl -l $_=pop;$?++\,!$&while/(.{$?})(?=.*\1)/;print$&
(notice the useless !$&) but fails like this:
#!perl -l $_=pop;$?++while/(.{$?})(?=.*\1)/;print$&
Migrated from rt.perl.org#19388 (status was 'resolved')
Searchable as RT19388$